1. Field of the Invention
The present invention pertains to a method and apparatus for heating thermoformable material in footwear such as an insole. More particularly, the present invention relates to a device for insertion into a piece of footwear where the thermoformable material is heated by the application of hot air, and the wearer's foot is inserted to form the heated insole at the contour of the foot. The device includes a form or mold which fits into the footwear and has apertures for directing the flow of hot air.
2. Description of the Prior Art
Various systems for producing custom insoles have been developed. For example, U.S. Pat. No. 3,895,405 to Edwards teaches an adjustable insole method in which an insole having a cushion layer and a foam cover is inserted into a shoe. A heat gun then applies heat to the insole. The wearer then places his or her foot into the shoe so that the insole conforms to the wearer's foot. The Edwards system has several limitations. First, the heat gun cannot evenly heat the entire insole. Second, there is no way to ensure that the end of the insole away from the opening will receive sufficient heating. Third, the Edwards patent does not disclose any way to heat any other portion of the inside of the shoe to create a custom inner surface.
Other systems for producing insoles are complicated and require considerable time to complete, as well as involve significant cost. U.S. Pat. No. 4,669,142 to Meyer shows such a method in which a cast is made of the wearer's foot, an insole is inserted into the cast where it is heated. The wearer then places his or her foot upon the insole in the cast so that it conforms to the foot. In addition to the foregoing drawbacks, the Meyer method does not allow for heating and conforming of other portions of the inside of the shoe or for insoles which extend along the sides and top of the foot. Similarly, since the insole is not heated inside the shoe, conformity of the insole to the inside of the shoe in addition to the shape of the wearer's foot, cannot be guaranteed.